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Wednesday, January 16, 2013

Future New Frontiers and Discovery Missions

Before I write my post on an upcoming planetary mission (promised in my last post), I wanted to complete my reporting on the Outer Planet Analysis
Group (OPAG) meeting last week and the portion of the Small Bodies Analysis Group (SBAG) that
I listened to Monday. These analysis
groups (with their Mars and Venus counterparts) review NASA's planetary science
program and provide feedback.

I picked up one key point in Monday’s meeting while listening to James
Green, the head of NASA’s planetary science program. In reviewing his program’s projected budget,
his team believes that it can start two additional New Frontiers missions ($1B
each) and a single Discovery mission ($500M) in the next ten years. The balance between the two programs is NASA's choice; for approximately the same funding it could select one New Frontiers and three Discovery instead.

The
Discovery program has been incredibly successful -- just look at the currently
operating MESSENGER mission at Mercury and the Dawn spacecraft that just left
Vesta headed for Ceres. However, many
of the easy (read inexpensive) exciting missions have been done.
And it is hard to fit an outer planets mission, and I suspect many potential
comet and asteroid rendezvous missions, in its budget.

Alfred McEwen at the University of Arizona proposed an Io Discovery
mission for the recently completed selection competition. He is also principle investigator for the
HiRISE camera on the Mars Reconnaissance Orbiter. McEwen provided a proposal to the OPAG
meeting to help make Discovery missions more competitive in future Discovery
selections. In the justification, he
said that the Discovery program as currently structured doesn’t provide
sufficient funding for outer planet missions with adequate budgetary reserves. (His proposal was to help mitigate this problem by
adjusting the Discovery cost cap by the length of time required to conduct the
selected mission.)

If that remains true, the Discovery program may remain an inner solar
system (say from Venus to the asteroid belt) program. However, in the last Discovery competition many Venus
missions were proposed but none made it as far as the finalists list,
suggesting that the next step for Venus may require a larger New Frontiers
class mission. NASA is
looking to fly approximately five new missions to Mars starting in 2017 (see my
previous post) outside of the Discovery program. So the single new Discovery mission may
target another inner solar system destination.

Two New Frontiers missions gives an outer solar system mission, a comet
sample return, a Trojan asteroid mission, and a Venus lander mission better chances of being selected. I don't know if NASA used this reasoning in laying out it's roadmap, but it's a balance between New Frontiers and Discovery that I agree with.

A couple of other points from the OPAG meeting:

I have often wondered why the Europa multi-flyby proposal (nicknamed
the Europa Clipper) has been estimated to cost $2B when ESA can fly a Ganymede
orbiter with Callisto and two Europa flybys for ~$1.2B and NASA estimates a
multi-flyby mission for Io would cost ~$1B.
The answer may be as simple as, “it’s the radiation”. In a recap of the multi-flyby Europa concept,
the presenter mentioned that the Jupiter Juno New Frontiers mission (perhaps $1B in 2015
dollars) will receive around 1/10th (worst case 1/3rd)
the radiation of the Europa mission. Those
thirty or so Europa flybys the Clipper would do would expose the spacecraft to
an incredible radiation load, and that may drive the cost difference compared
to the other missions.

The availability of plutonium 238 for power supplies for future
planetary missions has been a concern for the last several years. An update on the situation at the OPAG
meeting stated that NASA has on hand two additional Curiosity radioisotope
systems (MMRTGs), one of which will be used for the 2020 rover mission. The second set could be used by the Europa
mission or potentially another mission.
In addition, NASA continues to develop the next generation of power
supplies (ASRGs), and plans to have one available for a New Frontiers or
Discovery mission. However, the Pu-238
supply is becoming old and out of spec. It’s
essential that production of new Pu-238 begin to enable missions in the next
decade.

A closing note: Curiosity has
hit the jackpot, already. Water flowed
across its landing site, possibly multiple times. If you haven’t read Emily Lakdawalla’s post on the latest Curiosity news, I encourage you to do so.
Remember, this is just the start of what promises to be an incredible
stroll through Martian history. And we
can look forward to equally exciting locations for ESA’s 2018 ExoMars rover and
NASA’s 2020 rover to explore.

When I wrote the post, I wasn't sure of the status of the LEAG Lunar Exploration Analysis Group. NASA is ending it's lunar planetary science budget item. Lunar missions are still possible, but they would be funded through the Discovery and New Frontiers budgets.

Here's a link to the LEAG website: http://www.lpi.usra.edu/leag/meetings.shtml

I still don´t get it why an Europa multi-flyby mission is more expensive than a Io multi-flyby mission, since Io´s orbit is deeper in Jupiter´s radiation belt than Europa´s. So shouldn´t a Io mission be more expensive?

I´m also wondering if it would be possible to redirect Juno´s orbit for flybys of the Galilean moons in a possible extended mission.

TB -I'm not an expert on Jupiter's radiation fields, but I'll share what I understand. The intensity of the radiation varies with two factors: 1) the distance from Jupiter, with radiation increasing as you move closer to Jupiter*, and 2) your distance from the equatorial plane, with radiation highest in the equitorial plane and decreasing as you move toward the poles. Juno and the proposed Io Observer would have polar orbits, and therefore avoid the intense radiation except during the short time around when they pass through the equatorial plane. To get the ground tracks to cover the priority areas, however, the Clipper's orbits would be in the equatorial plane. So the total radition dose would be much higher. Also the Io Observer is typically spec'd for only ~6 flybys, and therefore again limits its radiation exposure. The Europa Clipper would do around 30 flybys of Europa meaning it will be bathed by radiation for a much longer period.

*Juno also uses one additional 'trick' to limit its radiation exposure. Very close to Jupiter, the radiation intensity drops dramatically. Juno will make its crossings of the equatorial plane in this gap.

There are also other probable drivers of costs for the Europa Clipper. It would gather and transmit far more data than either Juno or an Io Observer. More data equals more instruments, more power, better communications system, more data storage, etc., and all those factors also add costs. I haven't compared the data rates of ESA's JUICE mission with that proposed for the Clipper mission, but I suspect that JUICE may have lower data rates so that it could ratchet down all those corresponding cost drivers. However, that is speculation until someone does an apples and oranges comparison of the two missions.

I really would not get excited about Exomars just yet.According to Wikipedia, NASA was supposed to provide the landing system, based on the skycrane. This is a very complex piece of hardware and it's very unlikely that the Russians can provide something like that given their miserable recent track record. Wikipedia reports general skepticism too.As I have written before, ESA would be much better off cancelling the lander of ExoMars and use whatever money can be saved (plus more) try to organize a proper Titan mission. No radiation problems there (at least nothing like Europa) and it's a lot easier to land than Mars. The Russians should have the plutonium and experience to make the missing RTG.This, of course is not going to happen and ExoMars is likely to be postponed when reality sets in or simply fail.From what you have written, NASA has basically withdrawn from the outer solar system for a long while and we are condemned to an endless sequence of Mars missions and little else.Very, very bleak for solar system exploration, except, of course, for a single target.

I share your concerns about Russia developing a successful landing system for a medium sized lander after effectively being out of planetary exploration for so long. ESA's statements say that Russia will develop the landing system with "assistance" from ESA. Perhaps this will help Russia rebuild its expertise, but I worry about having the proof-of-concept on a Flagship mission.

NASA hasn't closed the door on outer planet exploration. (Or more correctly, the administration and Congress, which sets NASA's budget.) Any future missions will have to come through the New Frontiers program and possibly the Discovery program. This means that the missions will be limited in scope.

I like your idea of ESA creating a Titan exploration program. NASA could be a junior partner contributing the power systems and therefore also (under US law) the launches.

Technically, no, but New Frontiers ($1B) and Discovery ($500M) make only available about 1/2 and 1/4, respectively, of the amount of money required for a proper mission to Europa or Titan.Even TiME, as nice as it was, it was pretty limited.

"I like your idea of ESA creating a Titan exploration program"

NASA has provided the RTG to ESA before, with Ulysses, so it is not as crazy as it might look. The problem is that it would imply a re-organization and/or cancellation of a few ESA missions and ESA doesn't really do that. For better or worse, once they commit to a mission they go with it even when the money would be a lot better elsewhere (see Bepi-Colombo vs Messenger).

About Me

You can contact me at futureplanets1@gmail.com with any questions or comments.
I have followed planetary exploration since I opened my newspaper in 1976 and saw the first photo from the surface of Mars. The challenges of conceiving and designing planetary missions has always fascinated me. I don't have any formal tie to NASA or planetary exploration (although I use data from NASA's Earth science missions in my professional work as an ecologist).
Corrections and additions always welcome.